This invention relates to a mail processing apparatus, and more particularly to an address reading apparatus for a mail article, the apparatus being adapted to read the address description on either surface of the mail article.
A mail processing apparatus reads an address description on a mail article having various thicknesses. Two reading devices are frequently provided for reading both sides of a transfer path in order that address reading can be done regardless of which surface of the mail article is presented for reading.
A conventional address reading apparatus of this kind including two reading devices on opposite sides of a transfer path has a construction shown in FIG. 1. This apparatus comprises address readers 1 and 2 disposed in opposition to each other on both sides of a transfer path for reading an address description on a mail article. Pinch rollers 3 and 4 are disposed at the inlet and the outlet of the address readers 1 and 2. Pressure rollers 5 and 6 are disposed in contact with the pinch rollers 3 and 4. Guide plates 7 and transfer belts 8 and 9 form the transfer path. Address description detectors 10 and 11 are disposed on both sides the transfer path and upstream of the address readers 1 and 2.
The address description detectors 10, 11 detect the surface of the mail article on which the address description is written. To this end, the detectors 10 and 11 sense, for example, a postage stamp and a particular mark indicating the surface carrying the address description of the mail article. Therefore, before the mail article reaches the address readers 1 and 2, the system has detected which surface is carrying the address that is present on either the upward or the downward surface. When the mail article is transferred to a location between the address readers 1 and 2, it is held by a pair comprising the pinch roller 3 and the pressure roller 5 and by a pair comprising the pinch roller 4 and the pressure roller 6. The address description is read out by one of the address readers 1 and 2.
In FIG. 1, the pinch rollers 3 and 4 are rotated at fixed positions. The pressure rollers 5 and 6 are movably pressed against the rollers 3 and 4 by means of levers and suitable springs 12 and 13. Accordingly, when the mail article is held between the pinch rollers 3 (4) and the pressure rollers 5 (6), the pressure rollers 5 and 6 are moved in accordance with a thickness of the mail article.
In the above-described conventional address reading apparatus, the distance between the address reader 1 on the side of the pinch rollers 3 and 4 and a surface of a mail article is kept constant. However, the distance between the address reader 2 on the side of the pressure rollers 5 and 6 and the surface of the mail article varies by at least the thickness of the mail article since the pressure rollers 5 and 6 are moved away from their normal position in accordance with the thickness of the mail article. Therefore, the address reader 2 does not have a fixed distance focus upon the image of the address description formed on a scanning device via a lens. Accordingly, the address description cannot always be read accurately. Such a drawback is affected to a great amount, especially, when a mail article of 5 to 6 mm in thickness is processed.
It is possible to use an optical system having a deep focused range and having a mechanism for focusing a lens in accordance with the distance to the surface of a mail article to be read in order to overcome the drawback. However, such an optical system becomes complicated and expensive, and is not practical.